Methods for bonding a hermetic module to an electrode array

ABSTRACT

A method for bonding a hermetic module to an electrode array including the steps of: providing the electrode array having a flexible substrate with a top surface and a bottom surface and including a plurality of pads in the top surface of the substrate; attaching the hermetic module to the bottom surface of the electrode array, the hermetic module having a plurality of bond-pads wherein each bond-pad is adjacent to the bottom surface of the electrode array and aligns with a respective pad; drill holes through each pad to the corresponding bond-pad; filling each hole with biocompatible conductive ink; forming a rivet on the biocompatible conductive ink over each pad; and overmolding the electrode array with a moisture barrier material.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The subject disclosure relates to systems and methods forinterconnecting lead wires and bond pads, and more particularly to animproved biocompatible interconnection methods for attaching a hermeticimplantable bond pad array to a miniature flexible-circuit electrodearray and external lead wires.

2. Background of the Related Art

Various methods are used to interconnect hermetic modules, electrodearrays, and lead wires. Platinum wires co-fired with ceramic, laserwelding, anisotropic conductive film, thermo-compression bonding,electro-deposition, and plating up Platinum to form rivets are some ofthe approaches. Often the connection is to a hermetic Titanium enclosurewith electronics inside this hermetic volume.

Techniques for some examples are illustrated in U.S. Pat. No. 7,257,446issued on Aug. 14, 2007 to Greenberg et al., U.S. Pat. No. 7,480,988issued on Jan. 27, 2009 to Ok et al., U.S. Pat. No. 7,813,796 issued onOct. 12, 2010 to Greenberg et al., U.S. Pat. No. 8,285,380 issued onOct. 9, 2012 to Greenberg et al. and U.S. Ser. No. 13/490,189.

SUMMARY OF THE INVENTION

There are problems and drawbacks associated with the prior artapproaches such as poor interconnect density. The best prior art rivettechniques achieve two connections per square millimeter. There is aneed, therefore, for an improved method which permits increasedconnection density such as by an order of magnitude while insuringreliable and adequate connections.

In one embodiment, the subject technology interconnects a hermeticmodule bond-pad array (e.g., a medical implantable electronics module)to an electrode pad array and to external lead wires using micro-ink-jetor aerojet printing of bio-compatible conductive ink. In one embodiment,the ink contains Platinum. The method may use printed, bio-compatiblemushroom vias and/or laser forming of vias to get via sizes below 50microns, which allows a significant increase in connection density. Thesubject technology also includes a mechanically robust method ofconnecting to lead wires.

In another embodiment, the method for bonding a hermetic module to anelectrode array includes the steps of: providing the electrode arrayhaving a flexible substrate with a top surface and a bottom surface andincluding a plurality of pads in the top surface of the substrate;attaching the hermetic module to the bottom surface of the electrodearray, the hermetic module having a plurality of bond-pads wherein eachbond-pad is adjacent to the bottom surface of the electrode array andaligns with a respective pad; drill holes through each pad to thecorresponding bond-pad; filling each hole with biocompatible conductiveink; forming a rivet on the biocompatible conductive ink over each pad;and overmolding the electrode array with a moisture barrier material.

The pads may be annular. The hermetic module is attached to theelectrode array with a bio-compatible insulating adhesive. Preferably,the drilling of the holes is done by a laser and the holes aresubstantially circular and less than 50 microns in diameter. The methodmay also include the step of using an inkjet process to fill each holewith the biocompatible conductive ink.

In still another method for attaching a lead wire to a module frame,wherein the module frame including at least one module pad, includes thesteps of: drilling a hole in the hermetic module frame adjacent the atleast one module pad; feeding an electrode wire through the hole;securing the wire in place within the hole; connecting the at least onemodule pad to the hole and thereby the wire; and overmolding the aluminamodule frame. The wire may be secured by wrapping back onto itself andwelding. Connecting the at least one module pad to the hole and therebythe wire may be done by applying a printed conductive ink trace. Themethod can also include filling the hole with conductive epoxy, whereinthe epoxy is applied in a mushroom topology using an ink-jet or aerojetprinting process. The module frame preferably includes a plurality ofmodule pads and a plurality of corresponding holes with a feedthroughdensity greater than 2/mm². The method may also include the steps of:forming another module assembly according to claim 7 and stacking themodule assemblies; and providing a connective via between the twostacked modules.

A further method for bonding a hermetic module to an electrode array andattaching a lead wire thereto, wherein the electrode array including atleast one module pad, includes the steps of: providing the electrodearray having a substrate with a top surface and a bottom surface,wherein the at least one module pad is in the top surface of thesubstrate; attaching the hermetic module to the bottom surface of theelectrode array, the hermetic module having at least one bond-pad,wherein the bond-pad is adjacent to the bottom surface of the electrodearray and aligns with the at least one module pad; drilling a first holethrough the at least one module pad to the at least one bond-pad;filling the first hole with biocompatible conductive ink; forming arivet on the biocompatible conductive ink over the at least one modulepad; drilling a second hole in the electrode array and hermetic moduleadjacent the at least one module pad; feeding an electrode wire throughthe second hole; securing the wire in place within the second hole;connecting the at least one module pad to the hole and thereby the wire;and overmolding the electrode array and hermetic module. The electrodearray and hermetic module may combine to form a medically implantableelectronics module.

It should be appreciated that the present technology can be implementedand utilized in numerous ways, including without limitation as aprocess, an apparatus, a system, a device, a method for applications nowknown and later developed. These and other unique features of thetechnology disclosed herein will become more readily apparent from thefollowing description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those having ordinary skill in the art to which the disclosedtechnology appertains will more readily understand how to make and usethe same, reference may be had to the following drawings.

FIG. 1 is a top view of an electrode array in accordance with thesubject technology.

FIG. 2 is a cross-sectional view of the electrode array along line 2-2of FIG. 1.

FIG. 3 is a cross-sectional view of the electrode array of FIG. 1 afterattachment of a hermetic module in accordance with the subjecttechnology.

FIG. 4 is a cross-sectional view of the electrode array of FIG. 1 withdrilled holes in accordance with the subject technology.

FIG. 5 is a cross-sectional view of the electrode array of FIG. 1 withink filling the drilled holes in accordance with the subject technology.

FIG. 6 is a cross-sectional view of the electrode array of FIG. 1 theelectrode array overmolded to form a micropackage in accordance with thesubject technology.

FIG. 7 is a top view of an alumina module frame in accordance with thesubject technology.

FIG. 8 is a side view of the alumina module frame along line 8-8 of FIG.7.

FIG. 9 is a side view of the alumina module frame of FIG. 7 connectionbetween a lead wire and a module pad in accordance with the subjecttechnology.

FIG. 10 is a side view of the alumina module frame of FIG. 7 afterovermolding in accordance with the subject technology.

FIG. 11 is a top view of a substrate wafer with an array of modules inaccordance with another embodiment of the subject technology.

FIG. 12 is a perspective view of a single module 202 after readiness forseparation from the wafer is shown

FIG. 13 is a perspective view of a single module post singulationprocessing to prepare for connection to an electrode array.

FIG. 14 is a perspective view of a single module post singulationprocessing connected to an electrode array.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure overcomes many of the prior art problemsassociated with creating hermetic micropackages. The advantages, andother features of the systems and methods disclosed herein, will becomemore readily apparent to those having ordinary skill in the art from thefollowing detailed description of certain preferred embodiments taken inconjunction with the drawings which set forth representative embodimentsof the present invention and wherein like reference numerals identifysimilar structural elements.

All relative descriptions herein such as left, right, up, and down arewith reference to the Figures, and not meant in a limiting sense. Unlessotherwise specified, the illustrated embodiments can be understood asproviding exemplary features of varying detail of certain embodiments,and therefore, unless otherwise specified, features, components,modules, elements, and/or aspects of the illustrations can be otherwisecombined, interconnected, sequenced, separated, interchanged,positioned, and/or rearranged without materially departing from thedisclosed systems or methods. Additionally, the shapes and sizes ofcomponents are also exemplary and unless otherwise specified, can bealtered without materially affecting or limiting the disclosedtechnology.

Referring now to FIGS. 1-6, a series of figures depicting the steps forforming an electrode array and bonding a hermetic module to theelectrode array to form a hermetic micropackage 100 in accordance withthe subject technology is shown. The micropackage 100 is shown incross-sectional view in FIG. 6.

Referring now in particular to FIGS. 1 and 2, a top view andcross-sectional view along line 2-2 of an electrode array 110 inaccordance with the subject technology is shown. The electrode array 110includes a substrate 112 of a flexible circuit board such as KAPTON orPYRALUX materials available from DuPont or other desired polyimidelaminates. The substrate 112 has a top surface 114 and an opposingbottom surface 116. The electrode array 110 also includes a plurality ofpads 118 in the top surface 114 of the substrate 112. Each pad 118 isrectangular in shape with a central circular aperture 120. Not only isthe number and arrangement of the pads variable but the size and shapeis also variable depending upon the hermetic micropackage 100.

Referring now to FIG. 3, a cross-sectional side view of the electrodearray 110 is shown after attachment of a hermetic module 130 inaccordance with the subject technology. The hermetic module 130 includesa substrate 132 with a top surface 134 and a bottom surface 136. Aplurality of bond-pads 138 are embedded in the top surface 134.Preferably, the top surface 134 is substantially planar.

The top surface 134 of the hermetic module 130 is attached to the bottomsurface 116 of the electrode array 110 so that each bond-pad 138 alignsdirectly below a respective pad 118. Various attachment methods nowknown and later developed may be used to couple the electrode array 110and hermetic module 130 together. In one embodiment, the hermetic module130 is attached to the electrode array 110 with a bio-compatibleconductive adhesive 140.

Referring now in particular to FIG. 4, another cross-sectional view ofthe electrode array 110 with holes 142 is shown. The holes 142 areformed to extend from each pad 118 of the electrode array 110 to thecorresponding bond-pad 138 of the hermetic module 130. In oneembodiment, the holes 142 are laser drilled.

Referring now in particular to FIG. 5, a cross-sectional view of theelectrode array 110 with ink 144 filling the holes 142 is shownaccordance with the subject technology. Each hole is preferably filledwith biocompatible conductive ink 144 to form a connection from each pad118 of the electrode array 110 to the corresponding bond-pad 138 of thehermetic module 130. In one embodiment, an inkjet printing process isused to fill the holes 142 with the ink 144. The inkjet printing processcan also be used to form rivets 146 on the biocompatible conductive inkover each pad. The rivets 146 can be rounded to form a mushroom like topor other shape.

Referring now in particular to FIG. 6, a cross-sectional view of theelectrode array 110 after having been overmolded to form themicropackage 100 is shown. The overmolding process creates a moisturebarrier 148 for protecting the resulting assembly.

Referring now to FIGS. 7-10, a series of figures depicting the steps forattaching a lead wire to an alumina module frame 200 in accordance withthe subject technology is shown. Referring now in particular to FIGS. 7and 8, a top view and side view along line 8-8 of the alumina moduleframe 200 in accordance with the subject technology is shown. Thealumina module frame 200 includes various components shown but notlabeled for brevity and clarity. The alumina module frame 200 maycontain any number and arrangement of module pads 202.

Preferably, a laser (not shown) is used to drill through holes 204 inthe hermetic module frame 200. There may be a hole 204 provided for eachpad 202, one hole 204 may connect to multiple pads 202, or multipleholes 204 may connect to a single pad 202 as would be appreciated bythose of ordinary skill in the art based upon the subject disclosure.For simplicity, the following discussion relates to one hole 204connecting to one pad 204.

Still referring to FIG. 8, once the hole 204 is formed, an electrodewire 206 is fed through the hole 204. The electrode wire 206 is securedin place either by wrapping the wire 206 back onto itself or othermeans. When the wire 206 is wrapped back onto itself, laser or resistivewelding can permanently fix the wire 206 to itself. Preferably, theelectrode wire 206 is Platinum.

Referring now to FIG. 9, another side view of the alumina module frame200 of FIG. 7 is shown. In order to connect the hermetic module bond pad202 to the hole 204 and thereby the wire 206, a printed conductive inktrace 208 is applied. Another photo-patterned metal or the like may alsobe used as the ink trace 208. Typically, the ink trace 208 does not fillthe hole 204. Hence, the remainder of the hole 204 is filled withbio-compatible platinum conductive epoxy 210. In one process, the epoxy210 is applied in a mushroom topology using an ink-jet or aerojetprocess. Referring now to FIG. 10, a side view of the alumina moduleframe 200 is shown after overmolding in accordance with the subjecttechnology. Overmolding creates a moisture barrier 212 for protectingthe resulting assembly.

As will be appreciated by those of ordinary skill in the pertinent art,the subject technology provides many advantages. For example, itprovides a highly reliable electrode connection interface which isbio-compatible. Also, the channel count density (number of pads per mm²of surface area) can be substantially increased, which allows takingfull advantage of miniaturization afforded by integrated ultra-highdensity (i-UHD) packaging processes. Further, the through-hole lead-wireconnection does not rely upon adhesive bonding for shear-strength,enabling long-term electro-mechanical reliability. By usingnon-conductive adhesives to assure mechanical integrity, the conductiveink can be optimized.

By using the subject technology, reliable, bio-compatible interconnectsmay achieve a feedthrough density of greater than 2/mm². Assemblies maybe stacked with printed conductive via between two bonded modules. Thesubject technology is application to a wide variety of applicationsincluding in the commercial medical community such as in neuralstimulation and monitoring, augmentation of hearing and vision, andcardiac assist devices.

FIGS. 11-14 depicts one possible embodiment of the subject technology asa hermetic micropackage 200 interconnected to a high-density electrodearray 220 by a high-density interconnect lead wire 230.

Referring now to FIGS. 11-14, another series of figures depicting thesteps for forming an electrode array and bonding a hermetic module tothe electrode array to form a hermetic micropackage in accordance withthe subject technology is shown.

Referring now in particular to FIG. 11, a top view of a semi-conductorwafer 200 with an array of modules 202 is shown. Each module 202includes a main cavity 204 and a smaller secondary cavity 206. The maincavity 204 will contain the multi-chip module and the secondary cavity204 will facilitate interconnection to the multi-chip module One or bothof the cavities, 204, 206 may be etched as is well known in the art. Inanother embodiment, the secondary cavity 206 is formed using a laserdrill.

Referring additionally to FIG. 12, a perspective view of a single module202 is shown after completion of readiness for separation from thewafer. As such, the following description is with respect to the singlemodule 202 of FIG. 12 but would apply equally to all modules 202 on thewafer 200. While still integral with the wafer 200, the component 208 isattached in the main cavity 204. Interconnection posts 210 are securedin the secondary cavity 206. A multi-layer thin film interconnection 212operatively couples the posts 212 to thin film pads 215 of the component208. The thin film interconnection 212 may be printed or deposited by alift-off process. A hermetic bather coating 216 is applied to the top ofthe module 202 (e.g., the component 208) and, preferably, the back ofthe module 202 as well. At this point, the module 202 can be separatedor singulated from the wafer 200.

Referring now to FIG. 13, a perspective view of a single module 202 isshown post singulation processing to prepare for connection to anelectrode array 224 (see FIG. 14). The post singulation processingincludes welding wires or external leads 218 to the posts 210. Aflexible electrode 220 is glued to the module 202. The flexibleelectrode 220 includes a pattern of vias 222 aligned to feedthroughtraces 214 not coupled to the interconnection posts 210. The vias 222may be printed or laser drilled through the flex electrode 220. Theprinting method described above with respect to FIGS. 1-6 can beutilized to make connections to the feedthrough traces 214.

Referring now to FIG. 14, a perspective view of the single module 202 isshown connected to the electrode array 224. In one embodiment, theelectrode array 224 is a high-density flexible electrode array connectedto the active circuitry of the component 208 using the printed viaconnections as described above. High-density interconnect lead wires 226operatively couple the electrode array 224 to the printed vias 222. Theinterconnect lead wires 226 and the corresponding traces 214 can be flatmetal foil or thin-films. The resulting assembly is a hermetic activemicro-package 228. The micro-package 228 can be provided in a sealedenclosed made from a biocompatible material such as titanium.

As would be appreciated, alternate methods may be applied to the subjecttechnology without departing from the innovative concepts andstructures. For example, co-fired ceramic feedthroughs involve lowdensities and high temperature processing. Module thicknesses may belimited to greater than 1 mm thick using hybrid ceramic feedthroughmodules.

As would be appreciated by those of ordinary skill in the pertinent art,the functions of several elements as shown may, in alternativeembodiments, be carried out by fewer elements, or a single element.Similarly, in some embodiments, any functional element may performfewer, or different, operations than those described with respect to theillustrated embodiment. Also, functional elements shown as distinct forpurposes of illustration may be incorporated within other functionalelements, separated in different hardware or distributed in various waysin a particular implementation. Further, relative size and location aremerely somewhat schematic and it is understood that not only the samebut many other embodiments could have varying depictions.

INCORPORATION BY REFERENCE

All patents, published patent applications and other referencesdisclosed herein are hereby expressly incorporated in their entiretiesby reference.

While the invention has been described with respect to preferredembodiments, those skilled in the art will readily appreciate thatvarious changes and/or modifications can be made to the inventionwithout departing from the spirit or scope of the invention. Forexample, each claim may depend from any or all claims, even in amultiple dependent manner, even though such has not been originallyclaimed.

What is claimed is:
 1. A method for bonding a hermetic module to anelectrode array comprising: providing the electrode array having aflexible substrate with a top surface and a bottom surface and includinga plurality of pads in the top surface of the substrate; attaching thehermetic module to the bottom surface of the electrode array, thehermetic module having a plurality of bond-pads, each bond-pad beingadjacent to the bottom surface of the electrode array and beingconfigured to align with a corresponding pad; following the step ofattaching, drilling a plurality of holes through each of the pluralityof pads to its corresponding bond-pad, wherein each of the pads and itscorresponding bond-pad are connected in each of the holes; filling eachdrilled hole with biocompatible conductive ink; forming a rivet on thebiocompatible conductive ink over each pad; and overmolding theelectrode array with a moisture barrier material.
 2. The method of claim1, wherein the pads are annular.
 3. The method of claim 1, furthercomprising attaching the hermetic module to the electrode array with abio-compatible non-conductive adhesive.
 4. The method of claim 1,further comprising the holes by a laser.
 5. The method of claim 1,wherein the holes are substantially circular and less than 50 microns indiameter.
 6. The method of claim 1, further comprising using an inkjetor aerojet process to fill each hole with the biocompatible conductiveink.